An Edge Device (ED) is a device that sits on the boundary of layer-2 (L2) and layer-3 (L3) networks, and performs encapsulation and decapsulation of data from L2 to L3 and vice-versa. Generally, from a set of “capable devices”, that is, EDs that are capable of forwarding traffic for a given set of virtual local area networks (VLANs), an Authoritative Edge Device (AED) is an ED that is currently forwarding traffic for a given set of VLANs.
Unlike in L3 networks, where a momentary loop in a routing path is acceptable due to the concept of time-to-live (TTL), L2 networks cannot tolerate momentary loops. For example, such loops can destabilize the network leading to prolonged broadcast storms and network meltdown. Despite Spanning Tree Protocol (STP) L2 loop resolution, L2 virtual private network (L2VPN) over L3 technology demands multiple edge devices to have the ability to encapsulate and decapsulate data belonging to the same VLAN. This can cause L2 loops if there is even a momentary overlap of forwarding roles between two or more edge devices.